Process for preparing half ester acyl chlorides of aromatic dicarboxylic acids



United States Patent 9 Claims. (51. 260-475) The present inventionrelates to the production of half ester acyl chlorides of aromaticdicarboxylic acids, particularly of iso-and terephthalic acids.

The present application is an improvement over our copending applicationS.-N. 175,312, filed February 13, 1961. Our earlier process teaches theproduction of half ester acyl chlorides of aromatic dicarboxylic acidsandv their nuclear-substituted derivatives, particularly of isoandterophthalic acid, by heating the trich-loromethylbenzoic acid esters ofprimary aliphatic alcohols, preferably those having up to carbon atomsand particularly the methyl esters, with equimolecular amounts of thecorresponding methyl benzoic acids. This reaction is carried out in thepresence of small amounts of an acid catalyst such as iron (III)chloride, preferably in amounts of about 0.1% at higher temperatures,particularly IOU-160 C. and preferably 120 to 130 C. Subsequently, theresulting mixture of dicarboxylic acid half ester acyl chloride andmethyl benzoic acid chloride is separated by distillation.

It has now been found that the half ester acyl chlorides of benzenedicarboxylic acids which may, if desired, be halogen-substituted,particularly of isoand terephthalic acid, may be prepared particularlyadvantageously by heating the trichloromethylbenzoic acid esters ofprimary saturated aliphatic alcohols having up to 5 carbon atoms,preferably the methyl esters, with equimolecular amounts of thecorresponding benzene dicarboxylic acid monoesters in the presence ofcoordinately unsaturated inorganic polyhalogen compounds as catalysts inamounts of from 0.01 to 1.00% by weight. The preferred catalyst is iron('III) chloride or antimony (V) chloride. The reaction =is carried outat higher temperatures, particularly 50 to 160 C. and preferably 100 to130 C.

Two moles of the benzene dicarboxylic acid half ester acyl chloride tobe prepared according to the present invention are formed during thereaction, with the cleavage of 1 mole of hydrogen chloride, in an almostquantitative yield from one mole of the trichloromethylbenzoic acidester and one mole of the benzene dicarboxylic acid monoester. Sinceessentially no by-products are formed, the half ester acyl chloride maybe employed immediately for further treatment in many cases where noparticular requirements are manifested as to color and purity. How ever,the half ester acyl chloride may easily be obtained in a completelycolorless and pure condition by a relatively simple distillation.

The trichloromethylbenzoic acid esters required as starting material forthe reaction in accordance with the present invention are producedparticularly advantageous 1y from mor p-toluic acid methyl esters, ortheir halogensubstitution products, by chlorination under exposure tolight at temperatures above 150 C. to produce the trichloromethylbenzoylchlorides, which may be further reacted at once with alcohol to form theesters.

According to the present invention, esters of primary saturatedaliphatic alcohols are used as the trichl-oromethylbenzoic acid esters,for example, methyl-, ethyl-, propyl-, butyl-, and amyl-esters. Themethyl esters are preferably used since they react with the greatestspeed 0 reaction and in the most complete manner. I

As catalysts, in addition to iron (HI) chloride and antimony (V)chloride, zinc chloride, aluminum chloride and boron fluoride, forexample, may be used. These substances are designated as acid-analogoussubstances, for example, according to the Lehrbuch der OrganischenChemie by Klages, volume 2, second edition, page 124, and may be definedas cordinately unsaturated, inorganic polyhalogen compounds. 7

During the reaction according to the present invention, the half esteracyl chloride is formed within a short time with the cleavage ofhydrogen chloride. The reaction is generally completed after 1 to 2hours. The end of the reaction may be recognized by the cessation ofhydrogen chloride formation.

The benezene dicarboxylic acid half ester a-cyl chlorides are valuableintermediate products for the production of synthetic materials bypolycondensation.

It is an object of the present invention, therefore, to provide animproved process for the production of half ester acyl chlorides ofbenzene dicarboxylic acids, particularly of isophthalic acid andterephthalic acid.

This and other objects will become obvious from the following furtherdescription wherein the examples serve to illustrate the processwithout, however, limiting the same.

Example 1 253.5 parts by weight of p-trichloromethylbenzoic acid methylester and 180 parts by weight of terephthalic acid monomethyl ester areheated to 120 C., while stirring, with the addition of 0.4 part byweight of iron (III) chloride. A brisk hydrogen chloride cleavage startsat about C. After heating for two hours to -130 C., a clear brownsolution is formed, and the reaction mixture no longer evolves hydrogenchloride, even when the temperature is increased to C. By distilling invacuo, 363 parts by weight of terephthalic acid methyl ester chloridehaving a melting point of 54 C. are obtained at 15 torr at the boilingpoint of 140140.5 C.

Example II 25 3.5 parts by weight of m-trichloromethylbenzoic acidmethyl ester and 180 parts by weight of isophthalic acid monomethylester are heated to l20130 C. for one hour with the addition of 0.4 partby weight of antimony pentachloride. A brisk hydrogen chloride formationstarts at about 70 C. After completion of the reaction, 372 parts byweight of isophthalic acid methyl ester chloride are obtained bydistillation in vacuo at 12 torr at the boiling point of 144-146" C.

Example III 288 parts by weight of 4-chloro-3-trichloromethylbenzoicacid methyl ester are heated for one hour to 120- l30" C. with 214.5parts by weight of 4-chloroisophthalic acid monomethyl ester with theaddition of 0.4 part by weight of antimony pentachloride. A briskhydrogen chloride formation commences at 80 C. and upon terminationthereof the reaction mixture is distilled in vacuo. At 18 torr, 205parts by weight of 3,4-dichloroisophthalic acid methyl ester aredistilled at l78180 C., corresponding to a yield of 88% of thetheoretical yield. 1

Since certain changes may be made in carrying out the above processwithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

Since certain changes may be made in carrying out the above processwithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

We claim:

1. A process for the preparation of half ester acyl chlorides of benzenedicarboxylic acids and the nuclearchlorine substituted derivativesthereof which comprises reacting approximately equimolecular amounts of(I) an ester selected from the group consisting oftrichloromethylbenzoic acid esters of primary saturated aliphaticalcohols of from 1 to carbon atoms and nuclear-chlorine substitutedtrichloromethylbenzoic acid esters of primary saturated aliphaticalcohols of from 1 to 5 carbon atoms with (2) a corresponding monoesterof an organic acid selected from the group consisting of benzenedicarboxylic acids and nuclear-chlorine substituted benzene dicarboxylicacids with a primary saturated aliphatic alcohol of from 1 to 5 carbonatoms at an elevated temperature in the presence of a catalytic amountof a coordinately unsaturated inorganic poly-halogen compound.

2. The process of claim 1, wherein said inorganic polyhalogen compoundis utilized in an amount of from 0.01 to 1.00% by weight.

3. The process of claim 1, wherein both the trichloromethylbenzoic acidester and the monoester are the methyl ester.

4. The process of claim 1, wherein said inorganic polyhalogen compoundis selected from the group consisting of iron (III) chloride, antimony(V) chloride, zinc chloride, aluminum chloride, and boron fluoride.

5. A process for the preparation of half ester acyl chlorides of benzenedicarboxylic acids and the nuclearchlorine substituted derivativesthereof which comprises reacting an ester selected from the groupconsisting of trichloromethylbenzoic acidesters of primary saturatedaliphatic alcohols of from -1 to 5 carbon atoms and nuclearchlorinesubstituted trichloromethylbenzoic acid esters of primary saturatedaliphatic alcohols of from 1 to 5 carbon atoms with an approximatelyequimolecular amount of a corresponding monoester of an organic acidselected from the group consisting of benzene dicarboxylic acids andnuclear-chlorine substituted benzene dicarboxylic acids with a primarysaturated aliphatic alcohol of from 1 to 5 carbon atoms at a temperatureof from about to about 160 C. in the presence oftfrom 0.01 to 1.00% byweight of a coordinately unsaturated inorganic polyha-logen compound.

6. The process of claim 5,w-herein both the trichloromethylbenzoic acidester and the monoesterare the methyl ester.

7. The process of claim 5, wherein said inorganic polyhalogen compoundis selected from the group consisting of iron (III) chloride, antimony(V) chloride, zinc chloride, aluminum chloride and boron fluoride 8. Theprocess of claim 5, wherein the resultant half ester acyl chloride isadditionally purified by distillation.

9. A process for the preparation of half ester acyl chlorides of benzenedicarboxylic acids and the nuclear-chlorine substituted derivativesthereof which comprises reacting an ester selected from the groupconsisting of trichloromethylbenzoic acid esters of primary saturatedaliphatic alcohols of (from 1 to 5 carbon atoms and nuclear chlorinesubstituted trichloromethylbenzoic acid esters of primary saturatedaliphatic alcohols of from 1 to 5 carbon atoms with an approximatelyequirnolecular amount of a corresponding monoester of an organic acidselected from the group consisting of benzene dicarboxylic acids andnuclear-chlorine substituted benzene dicarboxylic acids with a primarysaturated aliphatic alcohol of from 1 to 5 carbon atoms at a temperatureof from about to about C. in the presence of from 0.01 to 1.00% byweight of a coordinately unsaturated inorganic polyhalogen compound.

References Cited by the Examiner UNITED STATES PATENTS 7/1934 Mills260544 10/1950 Rabjohn 260-544

1. A PROCESS FOR THE PREPARATION OF HALF ESTER ACYL CHLORIDES OF BENZENEDICARBOXYLIC ACID AND THE NUCLEARCHLORINE SUBSTITUTED DERIVATIVESTHEREOF WHICH COMPRISES REACTING APPROXIMATELY EQUIMOLECUALAR AMOUNTS OF(I) AN ESTER SELECTED FROM THE GROUP CONSISTING OFTRICHLOROMETHYLBENZOIC ACID ESTERS OF PRIMARY SATURATED ALIPHATICALCOHOLS OF FROM 1 TO 5 CARBON ATOMS AND NUCLEAR-CHLORINE SUBSTITUTEDTRICHLOROMETHYLBENZOIC ACID ESTERS OF PRIMARY SATURATED ALIPHATICALCOHOLS OF FROM 1 TO 5 CARBON ATOMS WITH (2) A CORRESPONDING MONOESTEROF AN ORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF BENZENEDICARBOXYLIC ACIDS AND NUCLEAR-CHLORINE SUBSTITUTED BENZENE DICARBOXYLICACIDS WITH A PRIMARY SATURATED ALIPHATIC ALCOHOL OF FROM 1 TO 5 CARBONATOMS AT AN ELAVATED TEMPERATURE IN THE PRESENCE OF A CATALYTIC AMOUNTOF A COORDINATELY UNSATURATED INORGANIC POLYHALOGEN COMPOUND.